Faculty Profiles - URITANI Akira

Papers - URITANI Akira

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Development of Novel Rare Earth Doped Fluoride and Oxide Scintillators for Two-Dimensional Imaging Reviewed

Vol. 29 ( 12 ) page： 1178-1182 2011.12

Language：English Publishing type：Research paper (scientific journal)

Two topics were focused. The first one was about the gamma-ray scintillator, Pr3+:Lu3Al5O12 (LuAG). The second one was about neutron scintillator, Ce3+:6LiCaAlF6 and Eu2+:6LiCaAlF6 (6LiCAF). Those scintillators have been developed very recently for modern imaging applications in the medical and homeland security fields. In both cases, the rare earth ions are playing the crucial role as emission centers. Pr3+ in LuAG provided fast 5d→4f transition providing noticeably shorter decay time than that of Ce3+. Among several candidate hosts, LuAG showed the best performance. Bulk crystal growth, basic scintillation properties, two-dimensional gamma-ray imaging and positron emission mammography (PEM) application were demonstrated. Due to the international situation, the homeland security was compromized by illicit traffic of explosives, drugs, nuclear materials, etc. and the ways to its improvement became an important R&D topic. For this purpose the Ce and Eu doped LiCAF appeared competitive candidates. Especially, when substitution of 3He neutron detectors was considered, the discrimination ability of gamma-ray from alpha-ray was important. Bulk crystal growth, basic scintillation properties and two-dimensional neutron imaging were demonstrated.

Development of Neutron Diagnostic Systems for LHD Deuterium Experiments

T. Iguchi, A. Uritani, N. Nishio, J. Kawarabayashi, K. Watanabe, A. Yamazaki, H. Tomita, M. Sasao, A. Okamoto, S. Kitajima, K. Ishii, T. Nishitani, K. Ochiai, M. Ishikawa, K. Shinihara, J. H. Kaneko, F. Fujita, H. Harano, T. Matsumoto, E. Takada, M. Isobe, T. Tanaka, K. Nishimura, H. Yamanishi and M. Osakabe

Annual report of National Institute of Fusion Science page： 219 2011.11

Study on Measurement of Total Neutron Yield during Deuterium Experiments and its Calibration

A. Uritani, N. Nishio, J. Yamazaki, K. Watanabe, H. Yamanishi and M. Isobe

Annual report of National Institute of Fusion Science page： 108 2011.11

A Study on Electron Density Imaging Using the Compton Scattered X-ray CT Technique Reviewed

Ryota Masuji, Kenichi Watanabe, Atsushi Yamazaki, Akira Uritani

Nuclear Instruments and Methods in Physics Research Section A Vol. 652 ( 1 ) page： 620-624 2011.10

Language：English Publishing type：Research paper (scientific journal)

We propose a novel electron density imaging technique based on a Compton scattered X-ray CT (CSX-CT)
technique. We design fundamental configuration of the CSX-CT system, which consists of a fan-shaped
X-ray beam, two-dimensional sensors for scattered X-ray detection, parallel plate collimators for limitation of the direction of scattered X-rays and a line sensor for the transmission of X-ray CT
(TX-CT). An image obtained by the TX-CT can be used to correct the attenuation effect of scattered X-rays.
Through Monte Carlo simulation modeling studies of the CSX-CT system, we demonstrate that the
utilization of the information of scattered X-rays is useful to obtain the electron density image. We
additionally confirm that the medical exposure irradiated in the CSX-CT is estimated to be lower than the maximum dose recommended in the guideline of some committees.

Neutron-Gamma Discrimination Based on Pulse Shape Discrimination in a Ce:LiCaAlF₆ Scintillator Reviewed

Atsushi Yamazaki, Kenichi Watanabe, Akira Uritani, Tetsuo Iguchi, Noriaki Kawaguchi, Takayuki Yanagida, Yutaka Fujimoto, Yuui Yokota, Kei Kamada, Kentaro Fukuda, Toshihisa Suyama, Akira Yoshikawa

Nuclear Instruments and Methods in Physics Research Section A Associated Equipment Vol. 652 ( 1 ) page： 435-438 2011.10

Language：English Publishing type：Research paper (scientific journal)

We demonstrate neutron-gamma discrimination based on a pulse shape discrimination method in a Ce:LiCAF scintillator. We have tried neutron-gamma discrimination using a difference in the pulse shape or the decay time of the scintillation light pulse. The decay time is converted into the rise time through an integrating circuit. A 252Cf enclosed in a polyethylene container is used as the source of thermal neutrons and prompt gamma-rays. Obvious separation of neutron and gamma-ray events is achieved using the information of the rise time of the scintillation light pulse. In the separated neutron spectrum, the gamma-ray events are effectively suppressed with little loss of neutron events. The pulse shape discrimination is confirmed to be useful to detect neutrons with the Ce:LiCAF scintillator under an intense high-energy gamma-ray condition.

Development of a Gamma-Camera with a Functional Collimator Reviewed

Kenichi Watanabe, Junichi Sugiyama, Atsushi Yamazaki, Akira Uritani

Nuclear Instruments and Methods in Physics Research Section AAssociated Equipment Vol. 652 ( 1 ) page： 582-586 2011.10

Development of a Compact Flat Response Neutron Detector Reviewed

H. Harano, T. Matsumoto, J. Nishiyama, A. Masuda, A. Uritani, K. Kudo

Vol. 58 ( 5 ) page： 2421-2425 2011.10

Language：English Publishing type：Research paper (scientific journal)

Long counters are widely used as neutron fluence monitors for their flat response. However, a bulky neutron moderator is required to achieve the flat response, which can be a disadvantage for portability and an undesirable source of scattered neutrons. Reducing the size of the moderator degrades the flat response, especially for high-energy neutrons. We propose a new method to reduce the size of the moderator while keeping a flat response, and we develop a compact flat-response neutron detector. The detector consists of two small spherical $^{3}$ He proportional counters embedded at appropriate positions in a compact cylindrical polyethylene moderator. The sensitivity ratio between the two counters was adjusted to provide a flat response in the total outputs from the two counters. We demonstrated by MCNPX calculations and response measurements for Cf and Am-Be neutrons and monoenergetic neutrons that the present detector had a sensitivity comparable to long counters with a good flat response in a wide energy range up to 20 MeV while being only one-fifth of the weight of long counters. The positions of the effective center were determined as a function of neutron energy. We also proposed a method to evaluate the neutron energy using the detector, which will allow various new applications taking advantage of the ability to measure neutron fluence and energy at the same time.

DOI： 10.1109/TNS.2011.2163191

Flat-response Neutron Detector Using Spatial Distribution of Thermal Neutrons in a Moderator Reviewed

Kenichi Watanabe, Junpei Otsuka, Musashi Shigeyama, Yousuke Suzuki, Atsushi Yamazaki, Akira Uritani

Nuclear Instruments and Methods in Physics Research Section A Vol. 652 ( 1 ) page： 392-396 2011.10

Language：English Publishing type：Research paper (scientific journal)

We propose a novel neutron detector that realized flat-response using information of a spatial
distribution of thermal neutrons in a moderator. The proposed detector consists of a 3He position sensitive proportional counter(PSPC) and a cylindrical moderator surrounding the 3He PSPC. The
cylindrical detector is irradiated by neutrons along the cylinder axis. The spatial response of the 3He
PSPC is used to correct the detector response in to flat-response. We adopt a weighting method to
achieve flat-response, in which detected neutrons weighted depending on their detected positions are
accumulated as the detector response. Through Monte Carlo simulation studies, we confirm that the
flat-response neutron detector can be realized by correcting the response of the proposed detector
using the weights determined by a multiple least squar emethod (MLSM). Additionally, fundamental
property of the 3He PSPC is experimentally investigated to check applicability to the proposed flat-response neutron detector. We conclude that we should take account of the end effect when
determining the weights and correcting the detector response.

Europium and Sodium Codoped LiCaAlF₆ Scintillator for Neutron Detection Reviewed

Takayuki Yanagida, Akihiro Yamaji, Noriaki Kawaguchi, Yutaka Fujimoto, Kentaro Fukuda, Shunsuke Kurosawa, Atsushi Yamazaki, Kenichi Watanabe, Yoshisuke Futami, Yuui Yokota, Akira Uritani, Tetsuo Iguchi, Akira Yoshikawa, and Martin Nikl

Applied Physics Express 4 (2011) 126402 Vol. 4 page： 106401-106403 2011.9

Study on the Calibration of LHD Neutron Monitoring System Reviewed

Naoto Nishio, Atsushi Yamazaki, Kenichi Watanabe, Akira Uritani, Mitsutaka Isobe and Hirokuni Yamanishi

Plasma and Fusion Research Vol. 6 page： 2405115-1 - 2405115-4 2011.8

Language：English Publishing type：Research paper (scientific journal)

Neutron monitoring is quite important because neutron yield generated by fusion reactions corresponds to
the fusion output. In design of the neutron monitor, Monte Carlo simulations play an important role to make
corrections on various parameters, such as neutron energy spectrum and spatial distribution when determining the calibration constant. We consider the calibration procedures using a Cf point source toroidally rotating in the vacuum vessel, and evaluate uncertainties of the calibration constant for the neutron detector placed on the center
axis.

Basic Study of Europium Doped LiCaAlF₆ Scintillator and its Capability for Thermal Neutron Imaging Application Reviewed

Takayuki Yanagida, Noriaki Kawaguchi, Yutaka Fujimoto, Kentaro Fukuda, Yuui Yokota, Atsushi Yamazaki, Kenichi Watanabe, Jan Pejchal, Akira Uritani, Tetsuo Iguchi and Akira Yoshikawa

Vol. 33 ( 8 ) page： 1243-1247 2011.6

New Idea of a Small-Sized Neutron Detector with a Plastic Fibre Reviewed

Tetsuro Matsumoto, Hideki Harano, Akihiko Masuda, Jun Nishiyama, Yoshinori Sakurai and Akira Uritani

Radiation Protection Dosimetry Vol. 146 ( 1-3 ) page： 92-95 2011.4

Absolute Measurement of Activity of ¹⁹⁸Au Foils Using the 4πβ–γ Coincidence Counting Method and Corrections by the Monte Carlo Simulation Reviewed

Jun Nishiyama, Hideki Harano, Tetsuro Matsumoto, Yasushi Sato, Akira Uritani and Katsuhisa Kudo

Radiation Protection Dosimetry page： 1-5 2011.3

Recent Activities on Neutron Standardization in Japan

Hideki HARANO, Tetsuro MATSUMOTO, Jun NISHIYAMA, Akihiko MASUDA, Akira URITANI, Katsuhisa KUDO

Progress in NUCLEAR SCIENCE and TECHNOLOGY Vol. 1 page： 138-141 2011

Thermal Neutron Calibration Method Using an Intense Neutron Beam from JRR-3M Reviewed

T. Matsumoto, H. Harano, J. Nishiyama, H. Matsue, A. Masuda, A. Uritani and K. Kudo

Radiation Measurements Vol. 45 ( 10 ) page： 1124-1126 2010.12

Language：English Publishing type：Research paper (scientific journal)

We have developed a thermal neutron calibration method using a reactor produced neutron beam in JRR-3M of the Japan Atomic Energy Agency. Neutron-induced prompt gamma ray analysis has usually been performed in this beam line. Neutron energy distributions with negligible contributions from epithermal neutrons were measured by a time-of-flight method with a chopper made of 6LiF powder. The thermal neutron flux was determined by a gold foil activation method. We found that the thermal neutron beam in JRR-3M was well suited for calibration, neutron detector development or neutron dosimetry.

A Study on the Neutron Monitoring System of LHD Based on Monte Carlo Simulations Reviewed

N. Nishio, S. Yamamoto, K. Watanabe, A. Uritani, M. Isobe, and H. Yamanishi

Review of Scientific Instruments Vol. 81 page： 10D-306-1-10D-306-3 2010.10

Language：English Publishing type：Research paper (scientific journal)

Neutron monitoring is quite important because fusion neutrons are a direct evidence of fusion reactions. In calibration experiments of a neutron monitoring system, Monte Carlo calculations play an important role to correct various effects. To perform Monte Carlo calculations for a helical type fusion device, we make a program that can automatically generate an input file of a helical coil geometry for the MCNP code. The neutron spatial distributions and spectra for the helical devices are calculated in the geometries automatically generated by this program. We also discuss in calibration experiments.

Fusion Product Diagnostics Planned for Large Helical DeviceDeuterium Experiment Reviewed

M. Isobe, H. Yamanishi, M. Osakabe, H. Miyake, H. Tomita, K. Watanabe, H. Iwai, Y. Nomura, N. Nishio, K. Ishii, J. H. Kaneko, J. Kawarabayashi, E. Takada, A. Uritani, M. Sasao, T. Iguchi, Y. Takeiri and H. Yamada

Review of Scientific Instruments Vol. 81 page： 10D-310-1-10D-310-5 2010.10

Language：English Publishing type：Research paper (scientific journal)

Deuterium experiment on the Large Helical Device LHD is now being planned at the National Institute for Fusion Science. The fusion product diagnostics systems currently considered for installation on LHD are described in this paper. The systems will include a time-resolved neutron yield monitor based on neutron gas counters, a time-integrated neutron yield monitor based on activation techniques, a multicollimator scintillation detector array for diagnosing spatial distribution of neutron emission rate, 2.5 MeV neutron spectrometer, 14 MeV neutron counter, and prompt -ray diagnostics.

中性子測定器の校正技術 Invited

松本哲郎、原野英樹、工藤勝久、瓜谷章

放射線 Vol. 34 ( 2 ) page： 101-109 2008.4

中性子標準のトレーサビリティーと国際相互比較 Invited

原野英樹、松本哲郎、工藤勝久、瓜谷章

放射線 Vol. 34 ( 2 ) page： 111-115 2008.4

Development of the Fast Neutron Standard Using a Be(α,n) Reaction at the National Metrology Institute of Japan Reviewed

T. Shimoyama, H. Harano, T. Matsumoto, K. Moriyama, T. Hata, K. Kudo, T. Koyamada, and A. Uritani

Radiation Protection and Dosimetry Vol. 126 page： 130-133 2007.8

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